Rotom

Rotom is a quite versatile Pokemon thanks to its solid typing both offensively and defensively, great Speed, and decent movepool. These traits allow it to perform well as either a Choice Scarf user or a Defogger. Electric / Ghost is a near unresisted typing, barring Shiftry, which can be pivoted out against with Volt Switch. Defensively, Rotom resists or is immune to various common attacks from Pokemon such as Archeops and Sandaconda, although has to watch out for common coverage moves such as Knock Off. Rotom's Speed allows it to outspeed threatening breakers such as Nasty Plot Mesprit and for its Choice Scarf set to outspeed other common Choice Scarf users like Mesprit. There are other Electric- and Ghost-types that give it competition as a Choice Scarf user, such as Togedemaru with its valuable Steel typing, and Haunter with its higher Special Attack alongside support moves such as Destiny Bond; both also have higher speed than Rotom. However, Rotom's unique type combination and access to both Trick and Volt Switch make it a great option over the other two.